Employing a technique called projection mapping, Dan Reynolds, Steve McGowan and their crew at Brave Berlin create a massive digital template of every nook and cranny of the Music Hall façade. Then they go to work, creating a video animation that manipulates movement, images and an ever-changing rainbow of colors.

At one point during last year's Lumenocity, the entire 136-year-old structure seemed to crumble to the ground, as if hit by a massive earthquake. At another, it became a giant elevator, spewing people across the face of the building when the "doors" opened. There were landscapes, too, and twirling kaleidoscopes.

For now, though, what will become a dance that sprawls for more than half a block along Elm Street is just three people in a dance studio: choreographer Johanna Bernstein Wilt, Cincinnati Ballet's artistic associate, and a pair of the company's principal dancers, Janessa Touchet and Cervilio Miguel Amador.

After just three weeks of sporadic rehearsals, they're about to commit the dance to film, the first step in converting it to a gargantuan digital display.

Reynolds and McGowan are here, too, along with Brave Berlin's graphic artist Kate Coslett. The intention is to film the ballet in front of a 60-foot by 30-foot "green screen." Later, the images of the dancers will be digitally isolated so that Reynolds, who is animating this section, can start working his particular magic on the images.

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It's 12:45 p.m. and a truck from Midwest Grip and Lighting shows up with the screen. Except that when two crewmen open the truck, it's empty. No one panics. But there is a palpable sense of anxiety. Is this an omen? Should we reschedule?

Rescheduling isn't an option, though. The show is less than five weeks away and every minute from here on out is accounted for. The drivers race back to the warehouse, pick up the drop and within 90 minutes everything is ready to go.

The filming goes without a hitch. And Reynolds and McGowan are elated by what they're seeing.

"Watching this gets me so emotional," says Reynolds. "She (Wilt) creates a beautiful love story in just three minutes."

The music helps, of course. The "Nimrod" section from Elgar's "Enigma Variations" is lush and richly romantic, a piece that tugs at even the hardest of hearts.

But near the end of the filming, Reynolds invites Wilt to take a look at the video. She's aghast. Because of the way the backdrop meets the floor, you can't see the dancers' feet.

From a dancer's viewpoint, it's a disaster. For Reynolds and McGowan, it's a revelation. Reynolds promises to do what he can with it.

"We want the same thing Johanna does," he explains later. "We want it to be amazing. I wasn't just trying to calm her when I said that. I will see if I can ... ." He pauses. It's obvious that he's not sure if it can be rectified. And now, of course, it's too late to re-shoot the ballet.

This is something new for Lumenocity. Last year's show included a smattering of animated human figures. But for the most part, they were graphic devices, used as part of a larger palette of visual images. This, on the other hand, is all about dance. And that, says Reynolds, is his major dilemma.

"We don't want the animation to overshadow the dance itself," he says. So basically, he has two choices. The first is to go simple, with two massive animated dancers on the building and limit the brash decorative hoopla. The other is to give the two dancing images the full animated treatment, with the background of the building pulsing and shimmering.

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The crew from Brave Berlin has set up shop in a temporary three-story tower on Race Street, just south of West 14th Street. It's directly across the sprawling Washington Park lawn from Music Hall.

Here, they have the computers that actually house the animation that we'll see next weekend. They also have 10 heavy-duty projectors, each cranking out a staggering 40,000 lumens of light. They're using the same sort of projectors that Twitter employed to create a huge Twitter feed wall in Cannes, France, last year and that the city of Boston used on New Year's Eve in Copley Square. But in Cannes, one projector was enough, and in Boston, it took two. This is 10 projectors.

"Yeah, it gives us pretty impressive options," laughs McGowan.

But what about that choreography? Did they decide to go simple or lavish? And did he find a way for us to see the dancers' feet?

"Yeah, about that," laughs Reynolds. He did find a way for us to see the dancers' feet. And as for the other? He still hasn't decided.

For the moment, he's leaning toward the simple approach, to focus on the dancing and make this short section a stark contrast with the rest of the show. But, he admits, it could still change at any moment.